The present invention relates to composite aircraft propeller blades, for example, of the general type disclosed in U.S. Pat. Nos. 4,407,635 and 4,524,499 assigned to the assignee of the present invention. The composite blade of the invention may be attached to a propeller hub component having an undercut or generally dove-tail shaped recess for receiving a root or base portion of the blade. The blade is ideally suited for use on a "propfan" aircraft which is powered by turbine engines each having counterrotating shafts which support and drive multiple blade fans or propellers. The blades for this type of engine have a substantial width to thickness ratio, and the width of each blade at its base is substantially greater than the rotatable hub component which retains the blade and changes the pitch of the blade.
It is important for each of the wide blades to be constructed with a predetermined bending stiffness and torsional stiffness to provide the desired strength while also avoiding flutter of the outer or tip portion of the blade. The blade should also provide for a smooth transfer of centrifugal and bending loads or forces resulting from propeller thrust and engine torque to the hub structure which retains and supports the blade and changes the pitch of the blade. Other forms of composite blades and their mounting structure are disclosed in U.S. Pat. Nos. 3,752,600 and 4,111,606.